in reply to Re: Re (tilly) 4: How NOT to do it
in thread How NOT to do it

It's that queries cannot be recursive. Of course, there have been a number of papers popping up here and there about Turing-complete SQL extensions.

antirice    
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Re: Re: Re: Re (tilly) 4: How NOT to do it
by Louis_Wu (Chaplain) on Sep 11, 2003 at 05:45 UTC
    It's that queries cannot be recursive. Of course, there have been a number of papers popping up here and there about Turing-complete SQL extensions.
    I can see how recursive queries could get rediculous, but why prevent that ability? Is it dangerous? Does it violate DB 'best practices'?

    I don't know much of anything about DB internals, or even the interfaces, so I'm groping here.

    *sigh* I just used a PHBism. Where's that lobotamy brochure?

    Perl programming and scheduling in the corporate world, as explained by dragonchild:
    "Uhh ... that'll take me three weeks, broken down as follows: 1 day for coding, the rest for meetings to explain why I only need 1 day for coding."
[reply]

      The reason is pretty simple: a database is a place to store and retrieve data. Creation of data is not up to the database. The database stores data and you ask it to present a relational view of the data stored based upon certain parameters. Regardless of how you relate the tables in your sql statement, you will get a finite amount of data back. Just for a wonderful nightmare, imagine a select statement that recursively inserted into the same table that it was selecting from. Of course, the fact that the database will return a finite amount of data is somewhat nice in my opinion.

      Hope this helps. If I made no sense, it's because I've been up for more than 24 hours :-/

      antirice    
      The first rule of Perl club is - use Perl
      The       ith rule of Perl club is - follow rule i - 1 for i > 1

[reply]

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